Universal modular tread and riser unit

A universal modular tread and riser unit for positioning on a stairway stringer having a predetermined slope, comprising:

• an elongate tread wall having two ends, including a connecting end and a free end;
• an elongate riser wall having two ends, including a connecting end and a free end;
• the riser wall having its connecting end joined to the connecting end of the tread wall with the riser wall oriented in a depending perpendicular relation to the tread wall;
• a pair of spaced apart side walls secured on either side of the joined tread wall and riser wall, the side walls spaced apart sufficiently to receive the stairway stringer with the free end of the tread wall resting on the stringer and the free end of the riser wall resting on the stringer;
• a tread sizing means including breakaway sections located at the free end of the tread wall for sizing the length of the tread wall between the ends of the tread wall;
• a riser sizing means including breakaway sections located at the free end of the riser wall for sizing the length of the riser wall between the ends of the riser wall;
• whereby the length of the tread wall and the length of the riser wall can be sized so that when the unit is positioned on a stairway stringer having a predetermined slope, the tread wall is oriented in a horizontal direction and the riser wall is oriented in a vertical direction.